1. Field of the Invention
The present invention relates to a coating dimension measurement apparatus that measures the dimension of a coating onto a sheet-like base material. Specifically, the present invention relates to a coating dimension measurement apparatus that performs coating dimension measurement that facilitates calibration.
Priority is claimed on Japanese Patent Application No. 2012-021574, filed Feb. 3, 2012, the content of which is incorporated herein by reference.
2. Description of the Related Art
All patents, patent applications, patent publications, scientific articles, and the like, which will hereinafter be cited or identified in the present application, will hereby be incorporated by reference in their entirety in order to describe more fully the state of the art to which the present invention pertains.
In a process of manufacturing process, for example, a capacitor electrode or a battery electrode, a material (coating material) for achieving particular electrical characteristics is painted (coated) onto a base material sheet (hereinafter, referred to as a sheet). In this case, although there are cases in which the coating material is coated over the entire surface of the sheet, in the case in which the coating material has a high cost or in which the coating material must not be coated onto the edge of the sheet, coating is done onto only a particular part of the sheet.
Such coating is known by terms such as partial coating, block coating, and pattern coating.
It is necessary to measure the coated part dimensions (width and length), and when coating both sides of a sheet, it is necessary to measure the dimensions (width and length) on both the front side and the rear side thereof.
FIG. 4 is a conceptual drawing showing an example of a coating pattern measurement apparatus in accordance with the related art. FIG. 4 shows the case of measuring a coating pattern by using cameras. In FIG. 4, a sheet 1 is supported by a transport roller (not shown), and is transported along a coating line at a constant speed. In the example of FIG. 4, the sheet 1 is moved to the left direction L. The sheet 1 has a sheet width W. A plurality of cameras 31 in which a lens 30 is mounted (two shown in FIG. 4) are installed over the coating line, and measure the coating dimensions on the sheet 1.
The sheet 1 moves to a determined direction (the left direction L in FIG. 4). Therefore, it is not necessary for the cameras 31 to have two-dimensional information when measuring the sheet 1. Therefore, line sensor cameras, which are arranged on a line that is perpendicular to the movement direction of the sheet 1 (the left direction L), are often used as imaging elements of the cameras 31. Of course, area sensor cameras that have two-dimensional information may alternatively be used as the image elements. In the example of FIG. 4, the cameras 31 measure a part of interest 33 in the coated part 32.
In the case of such a coating dimension measurement system, the following performance is required.
The sheet 1 is ideally transported past the same position on the transport line. When this occurs, depending upon the location of the coating line, the sheet 1 does not pass the completely same position, and varies up/down and left/right. The position where the sheet 1 is transported is referred to as a pass line. For example, if there is no support between transport rollers, there are cases in which the sheet 1 will vibrate up and down (with the pass line varying). It is necessary to prevent the position variation from influencing the measurement of the coating dimensions.
FIG. 5A is an oblique view of the main parts showing another example of a coating pattern measurement apparatus in which imaging is done above a transport roller in accordance with the related art. FIG. 5B is a cross-sectional view along the line A-A in FIG. 5A. In this coating pattern measurement apparatus, imaging is done above a transport roller at a position at which the sheet 1 does not vibrate up and down.
In FIG. 5A and FIG. 5B, the sheet 1 is supported by a transport roller 2 (hereinafter referred to simply as a roller 2). The sheet 1 is transported in the direction of the arrow B along the outer periphery of the roller 2. The cameras 31 each of which has a lens 30 are fixed to camera holding plates 31a. The camera holding plates 31a are fixed to setting collars 34 that are formed to be cylindrical. A shaft (camera holding shaft) 35 is inserted through the cylindrical parts of the setting collars 34. The cameras 31 are slidably and rotatably supported along the shaft 35, to which the cameras 31 are held by screws 35a (refer to FIG. 5B).
Illuminators 36 are fixed to illumination holding plates 37. The illumination holding plates 37 are held to the setting collars 38. A shaft (illuminator holding shaft) 39 is inserted into the cylindrical parts of the setting collars 38. The illuminators 36 is slidably and rotatably supported along the shaft 39 and held by the screws 39a (refer to FIG. 5B).
A scale (straight scale) 40 is disposed along the lengthwise direction of the roller 2 and is formed to be at least longer than the width W of the sheet 1, having a length along which all of the optical systems capture at one time. The cameras 31 capture the shape and the edges of the coating formed on the surface of the sheet 1. The cameras 31 are disposed at positions so that clear images are obtained. The illuminator 36 is disposed to give such angle that shadows of the illuminators 36 to the left and right of the imaging directions do not fall on the imaging positions.
In the above-described constitution, each of the optical systems are fixed by clamping to the shafts 35 and 39 via setting collars 34 and 38, thereby establishing the relative positioning between the sheet 1 and the cameras 31. As shown in FIG. 5A and FIG. 5B, the sheet 1 that is transported by the roller 2 is imaged when over the roller 2, and the dimension measurement is done from the captured image.
In FIG. 5A, there is an arrangement of four sets of image capturing optical systems and illumination optical systems disposed in a direction that is perpendicular to the flow direction of the sheet 1.
In general, the measurement of a coating width is done by positioning cameras 31 and capturing images at parts of interest (for example, a foil edge or coated part edge) the position of the parts of interest being determined from the position of the captured image. When this is done, if it is not possible with one camera to capture the overall image while maintaining the required resolution, a plurality of cameras 31, such as shown in FIG. 5A, are held at positions enabling image capture at the parts of interest, images of the parts of interest are captured with the required resolution, and the positions thereof are determined.
Because the distances between the cameras is fixed, it is possible to know the coated width from each of the positions. In this case, regardless of whether there is one or are a plurality of cameras, it is necessary to do numerical calibration so that, when a camera is positioned, it is possible to know what imaged position corresponds to how many millimeters. The most general method of numerical calibration is that of placing a scale (straight scale) 40 at a position equivalent to the sheet 1, as shown in FIG. 5A and FIG. 5B, and capturing images thereof to perform numerical calibration.
In cases in which the apparatus is such that it does not permit the location of a scale 40 at an equivalent position, the sheet 1 is measured by a width-measuring apparatus, and the obtained measurement value and a sample thereof are measured by a width-measuring apparatus having a higher accuracy by a different measurement method and one that can be correlated, that value being used as the basis for compensation and determination of the width.
Although there is no influence by the camera attitude or image capturing range if the overall range is captured by one camera, if a plurality of cameras 31 are used, the relative positions of each become important, and even if the cameras 31 are held fixed, there is no guarantee that loose screws or inadvertent contact will not disturb the fixed positions. For this reason, it is necessary to perform periodic checks.
Given this situation, consider the case in which calibration is performed by placing a scale 40 on the roller 2. Because damage to the roller 2 cannot be permitted, bringing a metal scale 40 up against the roller 2 is a very delicate process. Also, because the scale 40 is relatively long, the actual task is one of two persons supporting the scale 40 as the camera 31 is operated to capture images, making the task quite a troublesome one.
However, when the width-measuring apparatus is installed in tight quarters on a production line, this becomes an even more difficult task. Even if such a task is performed, the scale 40 is distanced from the surface of the roller 2 by the amount of its thickness (1 to 2 mm), this being optically magnified, leading to measurement errors.
Because of the above-noted situation, although numerical calibration is done at the time of camera installation, periodic calibration is not done that often. Although this is not a problem on a production line that always produces the same product, in which case the sheet 1 does not change, on a production line in which the product changes frequently, camera movement, numerical calibration, and the like become troublesome.
Additionally, even for one and the same product, if calibration is not done for a long period of time, it is difficult to characterize the production as having traceability. If the camera position or the lens position happens to change just a bit, it can result in products that are out-of-specification.
Accordingly, in the case of performing calibration by placing a scale on a roller, the present invention provides a coating dimension measurement apparatus that not only does not damage the roller, but also simplifies the calibration task.